Tibial tuberosity advancement (TTA) procedures are performed to treat deficient cranial cruciate ligaments in dogs. Currently used TTA procedures include the TTA Rapid™ procedure developed by Rita Leibinger Medical. This procedure allows an osteotomy to be made through a section of the proximal tibia allowing the tibial tuberosity to be advanced outwardly, the advanced tuberosity then held in position using a corresponding tibial tuberosity implant, typically in the form of a wedge. Such advancement of the tibial tuberosity stabilises the stifle joint by changing the angle of the patella ligament, and reducing tibiofemoral shear forces during weight bearing.
The TTA Rapid procedure includes the use of a saw and drill guide to assist the surgeon in correctly positioning the tibial osteotomy, allowing a first pin or drill guide to be inserted at the base of the osteotomy and a second pin at the top of the osteotomy at the proximate end of the tibia. Using this guide, the length of the osteotomy can be controlled and be reproduced exactly over a large number of surgeries. The angle of the osteotomy is typically an oblique angle from the longitudinal axis of the tibia and when using known saw guides, this angle is estimated each time the saw guide is positioned. By having to estimate the angle at which to place the drill guide, it is not possible to reproduce a successful surgery on further patients, and leaves the surgeon open to errors in judgement when placing the guide.
An osteotomy performed at an incorrect angle may result in patellar luxation, corresponding implants not having an optimal fit within the space provided, or may affect the degree to which the tuberosity is able to be advanced, as well as potentially jeopardising the long term success of the TTA operation.
The lack of consistency in the obliquity of the TTA osteotomies also makes it difficult to identify a full set of location parameters of the required osteotomy that may be reproduced across a range of animals.